The natural history of the pubescent child with blood pressures at or above the upper limits of normal has not been well defined. The purpose of this study is fourfold: 1) to determine the prevalence of hypertensive cardiovascular changes during adolescence; 2) to determine if the normal rise in blood pressures seen during puberty is related to sexual development; 3) to determine if the increased prevalence of hypertension in blacks becomes evident in adolescence; 4) to determine if exercise stress testing identifies those who are prone to develop hypertension. All eighth-grade children in the Dallas Independent School District currently have blood pressures recorded by school nurses. Eight hundred adolescents will be grouped according to stage of sexual development. Children having systolic or diastolic blood pressures in the upper 5th percentile will be recalled for repeat blood pressure determinations. Those with all three determinations the first year in the upper 5th percentile (and an equal number of controls) will have echo and vectorcardiograms to determine left ventricular hypertrophy, and some will have exercise stress tests to evaluate cardiac performance, i.e., echocardiographic determination of ejection fraction, pre-ejection period, ejection time and circumferential fiber shortening velocity, Blood pressures will be recorded semi-annually, and echocardiographic and vectorcardiographic studies annually. All patients in the initial follow-up group and the control students will be followed throughout the five-year period. All students will be rescreened bi-annually when in the tenth and twelfth grades. Blood pressure response to exercise stress testing and the echocardiographic and vectorcardiographic findings will provide data to determine the prevalence of hypertensive myocardial changes in adolescent children.